Help me make a 5 ah 74v Nano Battery

[biknut]

This is what I want to try to do, and I'm asking for your help. This will be my first attempt at making a battery, and I'm not planning to get too crazy at first. My plan is to make a 5 ah 74v Nano battery. It's just going to be an auxiliary back up in case I run out of juice before getting home. If it works well, I'll consider making another one to parallel together for 10 ah, and ultimately 15 or 20 ah.

I'm going to try to series 2 of these 37v battery's together to make one 74v 5 ah battery.



I think these will be able to discharge fast enough to power my Bomber without any trouble. Here's the specs.

Capacity: 5000mAh
Voltage: 10S1P / 10 Cell / 37V
Discharge: 65C Constant / 130C Burst
Weight: 1433g (including wire, plug & case)
Dimensions: 301 x 49 x 46mm
Balance Plug: JST-XH
Discharge Plug: 4mm Bullet-connector

The CA in my Bomber is set to 60 amp max, but I see it record about 64-65 amp regularly.

I hoping that if riding at a reasonable speed of 20 mph or less I'll get maybe 10-12 miles of range with a little reserve left over. The idea would be just to make it home.

I haven't ordered the battery's yet and it may in fact be a couple of months before I do, so right now we're just discussing the pros and cons of this idea, and I'm even open to a better idea if you can think of one.

Good areas of discussion would be about how to charge of this type of battery. I know nothing about that so far. Another thing I know nothing about for these battery's is about a BMS. Do these battery's even need such a thing? I'm thinking they don't.

One thing I do know is a lot of people complain that these battery's aren't very good. If you have experience with them, please share it with me.

It's possible that by the time I get ready to spend the money to buy them, I might decide to buy something different all together, so feel free to recommend a different plan if you feel so inclined.

 

[biknut]

I just learned how to calculate the C rate into how much amp draw a battery can withstand continuously. It's a lot easier then I thought.

it's, ah x C rate = amp draw

So in the example above we have 5 ah x 65c = 325 amp continuous drain

What that tells me is that battery is way over kill for a 65 amp Bomber. It would work fine, but I can use one that's a lot less expensive.

 

[motortriker]

From what I hear some rc toys can drain a battery in just a few mins.

That is what those batteries were designed for.

Max power, min weight. on rc toys.

They don't last long and tend to die in a fantastic way.

We bought 2 and one had a dead, shorted cell brand new.

Very hit or miss from the start using those batteries.

You already have a strong main pack that will deliver the big amps.

You would not have to use big amp high C cells for an extender pack.

The extender pack can be big or small too.

I use 18650 cell packs for extender packs.

 

[deacon]

way too complicated for me to figure but it seems a five amp hour would discharge 50amps at in five minutes or so.

 

[motortriker]

http://www.youtube.com/watch?v=vkDgoXikI_8

http://komar.in/files/A123packassy.pdf

This shows how cells are connected in a rc battery using A123 cells.

Lipo is the same but uses pouch cells instead of round ones.

 

[motortriker]

way too complicated for me to figure but it seems a five amp hour would discharge 50amps at in five minutes or so.

60C battery discharge

60mins * 1/60= 1 min discharge ? that's fast !

The wires on that battery would melt ?

 

[biknut]

What I'm finding out generally about these Nano battery's from Hobby King is they're usually way over rated. In other words 30c is really only 2c if you're lucky.

If I use one I'll probably need to buy the highest C rate offered, like the one I pictured above. That also means the most expensive.

Assuming that battery would be able to handle the 65 amp max current draw a Bomber is capable of putting to it, 2 of those battery's in series would be 74v 5 ah, with about 4 ah usable. That would be enough to go about 4 miles at wfo, or 10 miles at low speed.

the idea right now is just to explore how viable a battery like this would really be, without breaking the bank. I don't want to build a 20 ah battery, only to find out it can't handle the power drain.

I've read about peoples experiences trying to use 25c battery's and their conclusion was the battery couldn't handle a Bombers power demand for very many cycles, and there was a lot of voltage sag at full throttle.

 

[biknut]

So far I haven't seen where anyone tried using a 65c battery. I'm hopping such a battery might be at least 25c in reality, which would be enough.

Assuming success, which is expecting a lot, a 20 ah battery could be built for about $1600. The stock 18 ah battery is $2400, so it would be a substantial savings.

I'll tell you the truth, I expect it won't work, but I might be willing to invest in a 5 ah battery pack to find out.

 

[motortriker]

The people that use those and claim alot of cycles are very careful charging and discharging them.

Overcharging or over discharging them can kill them fast and they tend to die in a fantastic way.

HK sells alot of different tools for charging and discharging the rc lipo batteries.

They were designed for max power and lightest weight for rc toys.

They were not designed to last very long or die in a non fantastic way.

 

[biknut]

The people that use those and claim alot of cycles are very careful charging and discharging them.

Overcharging or over discharging them can kill them fast and they tend to die in a fantastic way.

HK sells alot of different tools for charging and discharging the rc lipo batteries.

They were designed for max power and lightest weight for rc toys.

They were not designed to last very long or die in a non fantastic way.

Yeah, a common complaint is about how high effort they are to charge, and maintain properly. Also short lifespan.

 

[biknut]

The general consensus about these Nano battery's is they can work ok if you consider them to be about half the C rating stated, and the burst rating to be half of that again. I'm hopping the problems people are reporting are caused by using battery's that aren't really powerful enough for the application.

For instance, a lot of people have tried using 40c battery's for a Bomber with poor results. A 5 ah 40c battery works out to 200 amps. On paper that would seem to be enough for a Bomber's 65 amp max draw. But if we half that amount it becomes 100 amp, and half again for a burst becomes only 50 amp. Not really enough.

I'm hopping the 5 amp 65c battery I would use will handle it. 5 amp 65c works out to 325 amp. Half of that would be 162.5, and half of that for a burst rating would be 81.25 amp. On paper that should be a safe margin.

 

[deacon]

I know i'm not to bright but how do you get it to put out that many amps for more than half a minute total. on a 5ah battery, before it drains the battery.

 

[biknut]

I know i'm not to bright but how do you get it to put out that many amps for more than half a minute total. on a 5ah battery, before it drains the battery.

I probably know less about than you do. I'm just basing that on what I get now from the stock battery. At wfo it's using about 4300 watts, and I'm getting slightly under 1 mile an ah. Of course that's about 50 mph, so 3 miles would take about 2.5 minutes.

 

[deacon]

okay sounds like you know what you are doing. I get less than one mile per amp hour at fifteen miles per hour but thats on sla. so I am trying to learn.

 

[biknut]

I probably know less about than you do. I'm just basing that on what I get now from the stock battery. At wfo it's using about 4300 watts, and I'm getting slightly under 1 mile an ah. Of course that's about 50 mph, so 3 miles would take about 2.5 minutes.

that math is off isn't it?

 

[deacon]

Here is what I thought.

Amp Hours is like the amount of gas in your car. You can trottle down and use up the gas or you can idle and use up the gas over a longer period of time. The trick is you have to have more gas in the tank to go farther. Way over simplified.

 

[biknut]

Here is what I thought.

Amp Hours is like the amount of gas in your car. You can trottle down and use up the gas or you can idle and use up the gas over a longer period of time. The trick is you have to have more gas in the tank to go farther. Way over simplified.

That sounds about right to me. My bike has a computer called a cycle analyst it provides a lot of information about your power consumption, and range.

What I've noticed it riding really slow and being careful with the throttle starting out from a stop I can get close to 5 miles an ah if I stay around 10-15 mph. Riding at full throttle it gets a little less than 1 mile per ah. Cruising about 20 mph uses about 2.75 ah per mile.

So you really can control your range with the throttle, but I like to go fast best lol. I want a big enough battery that I can go whatever speed I want, and get at least 40 miles. Thanks going to take about 40 ah.

 

[cannonball2]

Im no expert on this subject but I do have a lot of hands on with electric RC systems I have found the lipos to generally deliver close to what the are spec at. Research HobbyKing it a great learning tool. Check this motor, its a direct replacement for a 150cc 2stroke twin. Notice its max amps and the required 250amp speed control. Its lipos that are the power source. Don't give up yet!http://www.hobbyking.com/hobbyking/...Max_150cc_Size_Brushless_Outrunner_Motor.html

 

[cannonball2]

Heres a speed control to look at for fun. Notice the disclaimer for non RC use. http://www.hobbyking.com/hobbyking/store/__25608__Turnigy_Fatboy_V2_300A_ESC_4_15S_OPTO_.html

 

[snellemin]

For the heavy bomber I would use a minimum of 10ah pack. That 5ah will work, but will stress the controller out with the ripple current. 30-40C cells will be more than enough. There is no point of spending more money on cells that are overrated and won't be able to see a difference in performance on your bike.